1. Field of the Invention
This invention relates to an imaging apparatus. This invention particularly relates to an imaging apparatus, which is provided with an imaging device (an image detector) for recording an image as an electrostatic latent image.
2. Description of the Related Art
Apparatuses utilizing image detectors, e.g. facsimile apparatuses, copying machines, and radiation image sensors, have heretofore been known.
Methods and apparatuses for recording and reading out radiation image information by utilizing image detectors have heretofore been proposed. With the proposed methods and apparatuses for recording and reading out radiation image information, such that a radiation dose delivered to an object during a medical X-ray image recording operation maybe kept small, and such that the image quality of an image and its capability of serving as an effective tool in, particularly, the efficient and accurate diagnosis of an illness maybe enhanced, a solid-state radiation detector (an electrostatic recording material), which is provided with a photo-conductive material sensitive to radiation (such as X-rays), e.g. a selenium plate constituted of a-Se, or the like, is employed as an image detector. The solid-state radiation detector is exposed to radiation, such as X-rays, carrying radiation image information, and electric charges occurring in an amount proportional to the dose of the radiation delivered to the solid-state radiation detector are accumulated as latent image charges in a charge accumulating section formed within the solid-state radiation detector. In this manner, the radiation image information is recorded as an electrostatic latent image at the charge accumulating section. Thereafter, the solid-state radiation detector, on which the radiation image information has been recorded, is scanned with a laser beam or line light acting as reading light, and the radiation image information is thereby read out from the solid-state radiation detector. The methods and apparatuses for recording and reading out radiation image information by utilizing image detectors are described in, for example, U.S. Pat. No. 5,268,569, PCT International Publication No. WO 98/59261, Japanese Unexamined Patent Publication No. 9(1997)-5906, and Japanese Patent Application Nos. 10(1998)-232824, 11(1999)-242876, and 11(1999)-87922.
As described above, various electrostatic recording materials have heretofore been proposed as the image detectors. However, as for the technique for scanning the image detector with a reading electromagnetic wave and thereby reading out the electrostatic latent image from the image detector, no example has heretofore been disclosed wherein the technique is applied to a more practical apparatus.
For example, in the cases of a chest image recording apparatus, an image recording section of the chest image recording apparatus is moved vertically to a position matching with the position of an object, and an image recording operation is performed in this state. Therefore, it is necessary for the image detector acting as the image recording section to be capable of being moved vertically. Accordingly, in order for the image detector to be utilized practically in the chest image recording apparatus, or the like, it is necessary that the chest image recording apparatus, or the like, utilizing the image detector be small in size. Also, in cases where the image recording apparatus is to be utilized as a portable image recording apparatus, it is necessary that the image recording apparatus be small in size and portable.
Further, in cases where an image recording operation and an image read-out operation are to be performed by utilizing the a-Se photo-conductive material, such that a high radiation absorptivity may be obtained and such that an image with a high signal-to-noise ratio maybe obtained, a high voltage (of at least 1 kV) must be applied across the photo-conductive material. Specifically, in an ordinary image recording operation, it is necessary for the film thickness of the a-Se photo-conductive material to be at least approximately 500 xcexcm. In such cases, in order for an electric field intensity in the film to be kept, a voltage of at least 5 kV should preferably be applied across the photo-conductive material. Therefore, it is necessary for a high-voltage electric power source to be utilized for the image recording operation and the image read-out operation. However, in cases where a high voltage is applied across the image detector, if electrical insulation between a hot side and a grounding side is not good, arc discharge will occur, and reliability of a discharging section will become markedly low. Furthermore, strong noise will occur and will adversely affect the equipment. In cases where the image detector is to be utilized in the practical apparatus, it may be considered that the high-voltage electric power source located at the exterior of the apparatus be connected to the image detector via a cord and a connector. However, since the problems described above are encountered, the problems occur in that a special cord and a special connector must be utilized, and the cost of the apparatus cannot be kept low.
The primary object of the present invention is to provide an imaging apparatus provided with an image detector, which records image information as an electrostatic latent image and which generates an electric current in accordance with the recorded electrostatic latent image when being scanned with a reading electromagnetic wave, wherein the imaging apparatus is small in size.
Another object of the present invention is to provide an imaging apparatus, which is cheap in cost.
The present invention provides a first imaging apparatus, comprising:
i) a planar image detector, which records image information as an electrostatic latent image, and which generates electric currents in accordance with the electrostatic latent image when the planar image detector is scanned with a reading electromagnetic wave,
ii) a pre-exposure light source section, which is located at a position facing the planar image detector, and which irradiates a predetermined amount of an electromagnetic wave to an entire area of the planar image detector before the electrostatic latent image is recorded on the planar image detector,
iii) a reading exposure light source section, which is located between the planar image detector and the pre-exposure light source section, and which produces the reading electromagnetic wave and scans the planar image detector with the reading electromagnetic wave, and
iv) current detecting means for detecting the currents flowing out of the planar image detector in accordance with the electrostatic latent image, which has been recorded on the planar image detector, when the planar image detector is scanned with the reading electromagnetic wave,
the planar image detector, the pre-exposure light source section, the reading exposure light source section, and the current detecting means being accommodated within a single same case housing.
The present invention also provides a second imaging apparatus, comprising:
i) a planar image detector, which records image information as an electrostatic latent image, and which generates electric currents in accordance with the electrostatic latent image when the planar image detector is scanned with a reading electromagnetic wave,
ii) a pre-exposure light source section, which irradiates a predetermined amount of an electromagnetic wave to an entire area of the planar image detector before the electrostatic latent image is recorded on the planar image detector,
iii) a reading exposure light source section, which produces the reading electromagnetic wave and scans the planar image detector with the reading electromagnetic wave, and
iv) current detecting means for detecting the currents flowing out of the planar image detector in accordance with the electrostatic latent image, which has been recorded on the planar image detector, when the planar image detector is scanned with the reading electromagnetic wave,
the planar image detector, the pre-exposure light source section, the reading exposure light source section, and the current detecting means being accommodated within a single same case housing,
the reading exposure light source section also acting as the pre-exposure light source section.
The term xe2x80x9cimage detectorxe2x80x9d as used herein means the device capable of recording image information as an electrostatic latent image and generating electric currents in accordance with the electrostatic latent image when being scanned with the reading electromagnetic wave. By way of example, the image detector may be the electrostatic recording material described in Japanese Patent Application No. 10(1998)-232824. As the image detector, an image detector may be employed, which is capable of recording image information as an electrostatic latent image when being exposed to light (not limited to visible light) carrying the image information. Alternatively, an image detector may be employed, which is capable of recording radiation image information as an electrostatic latent image when being exposed to radiation carrying the radiation image information of an object.
The reading electromagnetic wave may be one of various kinds of electromagnetic waves, with which the electrostatic latent image is capable of being read out from the image detector. Specifically, the reading electromagnetic wave may be light, radiation, or the like. Therefore, the term xe2x80x9clight sourcexe2x80x9d as used herein means both the light source for producing light acting as the reading electromagnetic wave and the radiation source for producing radiation acting as the reading electromagnetic wave.
The term xe2x80x9cpre-exposure light source sectionxe2x80x9d as used herein means the light source section for irradiating the electromagnetic wave to the image detector in order to eliminate unnecessary electric charges accumulated in the image detector (i.e., for performing pre-exposure) before the recording light is irradiated to the image detector (as described in Japanese Patent Application No. 10(1998)-232824), or the light source section for performing primary exposure in order to conduct pre-charging (i.e., for performing pre-exposure) before final recording is performed. The wavelengths of the pre-exposure electromagnetic wave may be identical with the wavelengths of the reading electromagnetic wave, or may be different from the wavelengths of the reading electromagnetic wave.
Each of the first and second imaging apparatuses in accordance with the present invention should preferably be modified such that a high-voltage electric power source for applying a high voltage of at least 1 kV across the image detector is located within the case housing, and
the high-voltage electric power source is located in the vicinity of a connecting position of a grounding side and a connecting position of a hot side.
Also, the first imaging apparatus in accordance with the present invention, wherein the pre-exposure light source section and the reading exposure light source section are provided as two independent light source sections, should preferably be modified such that the pre-exposure light source section comprises:
a) a pre-exposure light source for producing the electromagnetic wave,
b) a reflecting plate located on one side of the pre-exposure light source, which one side is opposite to the side facing the image detector, the reflecting plate reflecting the electromagnetic wave toward the image detector, and
c) a surface-shaped filter, which is located between the pre-exposure light source and the reading exposure light source section and which transmits the electromagnetic wave having predetermined wavelengths.
Further, in the first imaging apparatus in accordance with the present invention, as the reading exposure light source section, a light source section for performing the scanning with a laser beam, a light source section for performing the scanning with line light, or the like, may be utilized. In particular, the first imaging apparatus in accordance with the present invention should preferably be modified such that the reading exposure light source section comprises:
a) a reading exposure light source, which is provided with a plurality of light emission points arrayed linearly, and
b) first optical means, which comprises a slit member having an opening area and an optical member for converging the reading electromagnetic wave to the opening area of the slit member, and which spatially filters the reading electromagnetic wave having been radiated out from each of the light emission points of the reading exposure light source, and
the reading exposure light source section operates such that the reading electromagnetic wave, which has been radiated out from each of the light emission points and has then passed through the first optical means, diffuses in a longitudinal direction of the reading exposure light source and impinges upon the image detector, and such that several reading electromagnetic wave beams, which have been radiated out from several light emission points among the plurality of the light emission points, simultaneously impinge upon an identical site on the image detector.
In such cases, the opening area of the slit member should preferably extend in the longitudinal direction of the reading exposure light source, and the optical member should preferably converge the reading electromagnetic wave, which has been radiated out from each of the light emission points, with respect to a direction normal to the longitudinal direction of the reading exposure light source. Also, the reading exposure light source section should preferably further comprises second optical means for converging the reading electromagnetic wave, which has passed through the first optical means, with respect to the direction normal to the longitudinal direction of the reading exposure light source.
The optical member of the first optical means described above may be constituted of SELFOC lenses, and the second optical means may be constituted of cylindrical lenses. Alternatively, the optical member of the first optical means may be constituted of cylindrical lenses, and the second optical means may be constituted of cylindrical lenses. Also, the reading exposure light source may comprise a plurality of LED chips arrayed linearly or a plurality of LD chips arrayed linearly. Alternatively, the reading exposure light source may be constituted of an LED array or an LD array.
Furthermore, the first imaging apparatus in accordance with the present invention should preferably be modified such that the image detector is supported by a surface-shaped base plate having permeability to light, the base plate being located on the side of one surface of the image detector, which one surface stands facing the pre-exposure light source section.
Also, each of the first and second imaging apparatuses in accordance with the present invention should preferably be modified such that a scattered ray removing grid is located at a position within the case housing, which position stands facing a side of the image detector opposite to a side facing the pre-exposure light source section.
Further, each of the first and second imaging apparatuses in accordance with the present invention may be modified such that the apparatus further comprises a support post for image recording, and
the case housing is supported by the support post for image recording such that the case housing is capable of being moved vertically.
Each of the first and second imaging apparatuses in accordance with the present invention, which are modified in such a manner, may be utilized for the recording of a chest image.
Furthermore, each of the first and second imaging apparatuses in accordance with the present invention may be modified such that the apparatus further comprises a support post for image recording, and a moving section supported by the support post for image recording such that the moving section is capable of being moved at least in one direction, which is among a vertical direction, a rotating direction, a horizontal direction, and a forward-reverse direction, and
the case housing is supported by the moving section (such as a U-arm or a C-arm).
With each of the first and second imaging apparatuses in accordance with the present invention, the image detector, the pre-exposure light source section, the reading exposure light source section, and the current detecting means are accommodated within the single same case housing. Therefore, the size of the imaging apparatus as a whole is capable of being kept smaller than the size of an imaging apparatus wherein an image detector, a pre-exposure light source section, a reading exposure light source section, and a current detecting means are accommodated within different case housings. Since each of the first and second imaging apparatuses in accordance with the present invention is formed compactly as the single case housing, the imaging apparatus is capable of being carried and moved easily and is suitable for use in practice.
Also, in cases where a high-voltage electric power source is located on the side outward from the case housing, a special connector and a cable must be utilized. Since the special connector, or the like, is expensive, the cost of the apparatus as a whole cannot be kept low. However, with each of the first and second imaging apparatuses in accordance with the present invention, wherein the high-voltage electric power source is located with in the case housing and in the vicinity of the connecting position of the high-voltage electric power source, the special connector described above need not be utilized, and the length of a cable is capable of being kept short. Therefore, the cost of the imaging apparatus as a whole is capable of being kept low.
The first imaging apparatus in accordance with the present invention, may be modified such that the pre-exposure light source section comprises (a) the pre-exposure light source for producing the electromagnetic wave, (b) the reflecting plate located on one side of the pre-exposure light source, which one side is opposite to the side facing the image detector, the reflecting plate reflecting the electromagnetic wave toward the image detector, and (c) the surface-shaped filter, which is located between the pre-exposure light source and the reading exposure light source section and which transmits the electromagnetic wave having predetermined wavelengths. In such cases, the pre-exposure of the image detector is capable of being performed efficiently. Also, with the pre-exposure, an image signal having a high signal-to-noise ratio is capable of being obtained.
In cases where a reading exposure light source section comprises a reading exposure light source, which is provided with a plurality of light emission points arrayed linearly, and an imaging apparatus may be constituted such that, for example, the light emission points and exposure points (read-out pixels) on an image detector correspond in a one-to-one relation to each other. In such cases, if the reading exposure light source is constituted of N number of light emission points, each of which corresponds to one exposure point on the image detector, and if it is defined that the imaging apparatus becomes inoperable when one of the light emission points malfunctions, a failure rate of the imaging apparatus will be represented by the formula shown below.
(Failure rate of apparatus)=(failure rate of light emission points)xc3x97N
Also, in such cases, if a mean variation of light emission amounts at light emission points is A% (and the areas of the exposure points are identical), a variation of exposure amounts at the exposure points on the image detector becomes equal to A%.
However, with the first imaging apparatus in accordance with the present invention, wherein the reading exposure light source section comprises the reading exposure light source, which is provided with the plurality of the light emission points arrayed linearly, and the reading exposure light source section operates such that several reading electromagnetic wave beams, which have been radiated out from several light emission points among the plurality of the light emission points, simultaneously impinge upon an identical site on the image detector, every exposure point on the image detector is uniformly exposed to the reading electromagnetic wave beams, which have been radiated out from, for example, M number of light emission points (Mxe2x89xa72). Therefore, even if one of the light emission points malfunctions and no electromagnetic wave is radiated out from the one light emission point, the exposure amount will decrease only by 1/M, and the malfunction of one light emission point does not directly cause a failure of the entire imaging apparatus to occur. Accordingly, the failure rate is capable of being kept lower than in the example of the imaging apparatus described above wherein the light emission points and exposure points correspond in a one-to-one relation to each other.
Further, in cases where the variation of the light emission amounts at the light emission points is A% (and the areas of the exposure points are identical), since each of the exposure points on the image detector is exposed to the reading electromagnetic wave beams, which have been radiated out from M number of light emission points, the mean variation of the exposure amounts at the exposure points on the image detector becomes equal to A/M% and thus becomes lower than in the example of the imaging apparatus described above wherein the light emission points and exposure points correspond in a one-to-one relation to each other.
Specifically, with the reading exposure light source section in the imaging apparatus in accordance with the present invention, the failure rate and the variation of the exposure amounts are capable of being kept low. Therefore, when a recorded image is read out, an image free from artifacts is capable of being obtained.
Furthermore, in cases where a service life and performance at least identical with the service life and performance of the conventional reading exposure light source section are to be exhibited, the service life of light emitting devices need not be so long as the service life of the light emitting devices employed in the conventional reading exposure light source section, and specifications with respect to the variation of the amounts of light radiated out from the light emitting devices may not be so strict as in the conventional reading exposure light source section. Therefore, the production yield of the light emitting devices is capable of being enhanced, and the cost of the imaging apparatus as a whole is capable of being kept low.
Also, the image detector may be supported by the surface-shaped base plate having permeability to light and an appropriate strength, the base plate being located on the side of one surface of the image detector, which one surface stands facing the pre-exposure light source section. In such cases, when the image detector, which is ordinarily formed on a markedly thin glass substrate, is located vertically, the image detector does not bend, and the image sharpness is capable of being kept high.
Further, the scattered ray removing grid may be located at the position within the case housing, which position stands facing the side of the image detector opposite to the side facing the pre-exposure light source section. In such cases, the scattered ray removing grid is capable of being combined compactly with the imaging apparatus. Also, the problems are capable of being prevented from occurring in that the image quality becomes bad due to radiation (scattered light) having been scattered by an object.